Two-stroke engine block



Sept. 13, 1932. F. LAGUEssE 1,876,977: A

Two-sTRoK ENGINE BLOCK Filed June 24; 1930 Patented Sept. 13, 1932 l UNITED STATES FERNAND LAGUESSE, or HEnsrAr., Bamm 'rwo-s'rno'xr. ENGINE BLOCK Application led June 24,1930, Serial 3o. 463,509, and in Belgium June 29, 1929.

Two stroke engines are known having opy posed pistons which respectively control the opening of the admission and exhaust ports and one of which is rigid with the piston of a K6 charging pump coupled toadelive'ry chamber or reservoir. In the known arrangements exn`- auxiliary chamber or clearance space which l 2 is connected to the cylinder of the pump by a relatively long duct. This auxiliary chamber or these auxiliary chambers in the caseof a.v

multi-cylinder engine can be arranged in the crank case itself.` Under these conditions a column of compressed gas is obtained in this duct which forms an accumulator not only neutralizing the4 partialsvacuum resulting from both the reversal in direction and movement of the compressor piston and the fall in 3 static pressure of the gas when the compression chamber is emptied but permits an increase in the pressure of the gasto be obtained A sion of the fresh compressed gases through by a dynamic eifect, which increases the eiliciency of the engine. v The fuel is admitted into the auxiliary chamber by means of a rotary distributor for example which, according to the invention is directlyadjacent this chamber for the purpose of obtaining continuity of the movement a of the column of gas contained in the duct connecting this chamber to the cylinder.

The accompanying drawing illustrates by way of example, one mode of construction of the invention. The form of construction chosen is particularly suitable for application to a motor cycle. Figure 1 is a general diagrammatic section of of an engine cylinder and its casingconstructed according to the invention.

Figure 2 shows certain diagram outlines.

In Figure l, atwo-stroke engine cylinder 2 guides the movement of two opposed pistons 3 andc4.coupled by rods 5 and 6 to the corresponding crank pins of a crank shaft 7. The cylinder 2 comprises at its upper part a part v2a bored toa larger diameter thanthat of the cylinder 2 inV which bore moves a. piston 3a' rigidwiththepiston 3. The s stem formed by the piston 3a and the cylin er 2a is designed to perform the function of a com- 00 pressor. Y During the downward lmovement of theA piston 3a and under the action of the resulting suction,air isdrawn in through a carburettor by the communication of the cylinder 3a through'a duct 45a`with the chamber 45o of a rotary distributor 46 of any known, type, .the chamber k4572 being for example placed -in direct communication with ythe carburettor. 7 During the upward stroke of the piston 3a corresponding to the ipower stroke of the pis- -ton 3 and after the closure of the duct 45a by the distributor 46, the carburetted mixture is compressed in the dead space ofthe cylinder 3a and .in a duct 2bl adapted to lead the freshgases towards the admission portk 2c in the power c linder theY opening of which port is controlled by the movement of the piston 3. f l

The operation of the engine takes lace upon the known cycle consisting in an a misthe port 2c`towards the end of themutual separation of the pistons 3 andi/l, the com- 85 pression of these gases during the movement of the said piston towards each other, the ignitionof the gases by va sparkingplug 8 towards the end cf'this inward movement, the expansion ofthe gases producing the power stroke of the pistons 3 and 4, the dischargeof the burnt gases through the exhaust port 2d towards the end of this power stroke, the scavenging of the burnt gases by the new charge of fresh gas admitted, askindicated above, and so on. During this admissionstage in which the fresh gases enter the cylinder, the pressure to the right ofthe port` 2c varies between two` determined limits. It is a maximum at 10 the commencement of the admission and a minimum under the iniiuence of the partial vacuum produced by the reversal of the direction of travel of the piston 3a, and by the throttling of the transferring orifice. It is Without doubt that the rational filling of the cylinder must be obtained when the pressure of the gases at 2c is approximately constant.

The arrangement provided according to the invention for suppressing these oscillations in pressure and rendering uniform the supply by bringing the pressure to a substantially constant ratio, and as near as possible to the pressure at the end of the compression, consists in providing an additional compression chamber 9 connected to the clearance space of the cylinder 2a by a duct 9a. In this way a column'of compressed gas is obtained in the latter forming what may be called a feeder, and the initial force of which will tend to neutralize the depressions undergone by the fresh gas during the period of opening of the port 2c. In this way a filling stage of the cylinder Q is obtained which is as uniform as possible. Naturally' the volume of the chamber 9 which is indispensible for supplying the duct 9a and also the section and length of the latter, are chosen in such a way as to ensure that the desired result will be obtained. y

As shown in Figure l, this chamber 9 and the duct 9a are connected between the rotary distributor and the compressor cylinder. Their arrangement at another point will remain moreover within the scope of the invention.

With a View to a possible regulation, the device shown in Figure 1 represents a member 10 in the form of a valve the position of which with respect to a seating 10a is adjustable in such a Way that it is possible to obtain at this point a certain throttling of the section of the duct 9.

The diagrams shown in Figure 2, of which only the general outline must be taken into consideration, enable the operation to be observed. i

In this figure the abscissae correspond to the angular displacement of one of the crankpins and the ordinates correspond to pressure to the right of the admission port for the curves @4b-J, a--b-e, a--b-Jn. The curve g-il-h represents the law for the opening and closing of the port 2e. Previous to the opening at the end of the upward stroke of the piston 3a the compression of the fresh gases in the cylinder 2a is completed in accordance with the curve a-b immediately before the commencement ofV the opening stage. In the case of a compression chamber of simple form, the expansion stage corre'- sponding to the period of opening of the admission port such as 2c will be represented by a curve b-d which will be extended by a part such as d-e if the opening of the port continued with a constant value. As this aperture commences to be throttled after this point i at the same time as the change Iin direction of movement of the compressor piston accentuates the expansion effected, the curve b-cZ is extended actually by the part d-f.`r^

By means ofthe arrangement invented, the curve representing the expansion during the admission period is raised, as shown by the curve b-fm/-wa It is seen that for one and the same initial pressure the final pressure is greater than in the other cases envisaged. corresponding tothe known devices with a compression chamber of simple form. On account of the raising of pressure indicated, the case whenlthe cylinder is filled at a constant pressure is more nearly approached, that is to say more favourable conditions are obtained.

Having now particularly described andv ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. A two-stroke combustion engine comprising a motive cylinder having admission and exhaust ports, two opposed pistons arranged in said cylinder so as to respectively control said admission and exhaust ports, a crankshaft operatively connected with both pistons, a pump piston formed by anenlargement of the piston controlling said admission ports, a cylinder for said pump piston formed by an enlargement-of said motive cylinder, which pump piston and cylinder form a charge introducing pump, an auxiliary chamber forming the principal part of the total compression space of the pump, which chamber is situated before the pump, and a relatively long duct connecting said auxiliary 'chamber with the pump cylinder.

2. A two-stroke combustion engine comprising a casing, a motive cylinder having admission and exhaust ports, two opposed pistons arranged in said cylinder so as to respectively control said admission and exhaust ports, a crankshaft operatively connected with both pistons, a pump piston formed by an enlargement of the piston controlling said admission ports, a cylinder for said pump piston formed by an enlargement of said motive cylinder, which pump piston and cylinder form a charge introducing pump, an auxiliary chamber forming the principal part of the total compression space of the pump, which chamber is situated in the engine casing before the pump, and a relatively long duct connecting said auxiliary chamber with the pump cylinder. f k' 3. A two-stroke combustion engine comprising a motive cylinder having admission and exhaust ports, two opposed pistons arranged in said cylinder so as to respectively control said admission and exhaust ports, a

' ment of the piston controlling said admission ports, a cylinder for said pump piston formed by an enlargement of said motive cylinder, which pump piston and cylinder' form a charge introducing pump, an auxili ary chamber forming the principal part of the total compression space of the pump,

which chamber is situated before the pump,V

a relatively long duct connecting said auxiliary chamber with the pump cylinder, and a :fuel distributor, directly adjacent said chamber to obtain continuity of movement of the column of gas contained in the duct connecting the chamber to the pump cylinder.

Dated this 6th day of May 1930.

FERNAND LAGUESSE. 

